Flexible drive devices are used in many applications to transfer motive force from a motor or other actuator to a moving load. Such drive devices employ tension members such as belts, cables or wire ropes to pull the load in its desired path of movement. These tension members are often driven by pulleys attached to rotary motors. Rotation of the motor causes rotation of the drive pulley which, in turn, causes movement of the tension member and its attached load. Flexible drive devices are particularly adapted to applications requiring reciprocating movement. One such reciprocating application is a cartridge handling apparatus of an optical disk storage and retrieval system. Magneto-optical disks and other types of optical disks are commonly used for storing musical works, audio-visual works, and computer-readable data. Such optical disks may be mounted in parallelepiped-shaped cartridges for purposes of storing and handling the disks.
For large databases consisting of many disk or tape cartridges, a cartridge handling system may be provided for handling and storing the cartridges. Various features and components of cartridge handling systems are disclosed in U.S. Pat. No. 4,998,232 issued Mar. 5, 1991 of Methlie, Oliver, Stayely, and Wanger; U.S. Pat. No. 5,062,093 issued Oct. 29, 1991 of Christie, Wanger, Dauner, Jones and Domal; U.S. patent application Ser. No. 08/491,286 of Schmidtke, Coffin, Paul, and Christie for MEDIA CARTRIDGE INSERTION APPARATUS FOR A MEDIA CARTRIDGE STORAGE AND HANDLING SYSTEM, filed on the same day as this application; and in U.S. patent application Ser. No. 08/491,538 of Paul and Smith for DOOR ASSEMBLY FOR A CARTRIDGE HANDLING DEVICE, filed on the same day as this application, which are hereby specifically incorporated by reference for all that is disclosed therein. Optical disk cartridge handling systems are generally referred to in the industry as "autochangers" or "optical disk juke boxes".
In general, a cartridge handling system may include a cartridge carrier for transporting cartridges between a user interface position located at the exterior of the storage and handling system and a system interface position located at the interior of the storage and handling system. The cartridge carrier may be reciprocally displaced between these two positions by one or more elongate flexible members (e.g., cables, belts, bands, or the like) under tension. Generally, each elongate flexible member is initially placed under tension upon mounting of the flexible member within the system, and that tensile force is maintained by applying a biasing force to the flexible member. Such a biasing force may be provided, for example, by including a biasing device in association with pulleys upon which a flexible member is mounted. In many flexible drive member applications, and particularly in the cartridge handling systems described above, space is severely limited. Accordingly, biasing devices for use in such systems must be extremely compact and efficient.
Various features and components of flexible member tensioning devices are disclosed in U.S. Pat. No. 5,232,407 issued Aug. 3, 1993 of Wolf and Boyd and in copending U.S. patent application Ser. No. 08/254,049 filed Jun. 3, 1994 of Luffel for FLEXIBLE MEMBER TENSIONING APPARATUS, which are hereby specifically incorporated by reference for all that is disclosed therein.
In a flexible drive system, such as a wire rope drive system, it is important that proper tension be maintained in the wire rope as the device operates.
In either direction of movement, the driven portion of the wire rope is pulled along due to frictional contact between the wire rope and the rotating drive pulley of the motor or other actuating device. The amount of force that can be transferred to the wire rope by the motor is directly dependent upon the amount of frictional force available. To achieve adequate frictional force, it is desirable to maintain proper tension in the slack side of the wire rope. This tension ensures that the wire rope will maintain contact with the motor drive pulley. Such tension is also desirable to ensure that the wire rope does not become lose enough to "derail" from either the drive pulley or from one or more idler pulleys located within the system.
It is, therefore, desirable to locate a spring or other type of tensioning device on the slack side of a wire rope. It is generally undesirable, however, to locate such a tensioning device on the driven side of the wire rope. On the driven side, a direct non-resilient connection is desirable between the motor and the load in order to provide maximum motive force.
This presents a problem since, in a reciprocating drive system, the slack side and the driven side switch positions each time the drive system reverses. Accordingly, a conventional type of tensioning device will be located on the driven side during at least one direction of travel.
Thus, it would be generally desirable to provide an apparatus which overcomes these problems associated with flexible drive member tensioning devices.